Abstract: To investigate the relationship between the distribution of zooplankton and environmental factors in the heavily polluted Liangtang River, the water quality and spatial distribution of zooplankton were studied from June to August, 2014. The trophic state of the sampling sites was evaluated using the trophic status index (TSI), and the relationship between zooplankton populations and environmental factors was analyzed using principal component analysis (PCA) and linear regression. The impacts on Shannon-Wiener diversity index were discussed. The results show that the Liangtang River should be classified as a hyper-eutrophic river, with the TSI index at all sampling sites higher than 70. Twenty-three species of crustacean zooplankton were identified, which included 15 species of 13 genera of cladocerans and 8 species of 8 genera of copepods. The biomass percentage of the total crustacean zooplankton was 53.17% cladocerans and 46.83% copepods. The dominant species of crustacean zooplankton were Diaphanosoma brachyurum, Moina micrura, Bosmina longirostris, Thermocyclops taihokuensis and Mesocyclops leuckarti. According to the results of PCA, the sections of the Liangtang River can be divided into three groups. Moina micrura was dominant exclusively in reaches of Liangtang River with high ammonia nitrogen (NH₄⁺-N) concentrations (1.80-6.27 mg/L), of which the biomass was up to 0.46 mg/L, while in reaches with high concentrations (79.20-92.10 μg/L) of chlorophyll a, Diaphanosoma brachyurum was the dominant species in zooplankton, of which the biomass was 0.30 mg/L. The Shannon-Wiener diversity for zooplankton was negatively dependent on transparency and concentration of chlorophyll a, of which the regression equations were y=-3.3x+4.22 and y=-0.015x+4.20, respectively. The present study highlights the importance of NH₄⁺-N, chlorophyll a concentration and zooplankton Shannon-Wiener diversity index for water quality assessment in the Liangtang River.